well the 4 link on my jeep kept the axle from rotating ..it stayed pointing the same general direction ...i wouldnt think that the pinion angle would be to crutial as long as its as close as possibe to where u think it sahould be ...however if you know the tranny you want you could get the dimentions of it and cut up a cardboard cutout of it ..then use that as yoru referance...also ..isnt the 4 link adjustable? well im just rambling some ideas from what i might do ..but there are lots of smarter pl on this site that can point you in a better direction im sure ..good luck